Extraction element layout Extraction parameters Current status of

4/01/2004 Run II Meeting

Dave Johnson 1

Extraction element layout Extraction parameters Current status of

•8 Gev interaction with other cycles•Tune Stability•Efficiency (losses/apertures), etc•Spill issues

How does Resonant extraction fit within the Program?

What is needed?How to accommodate?

Where do we go from here? Will NOT discuss beamline optics issues…

Operational Status of Resonant Extraction

Beams-doc-1102-v1


Dave Johnson 2

Extraction Straight

MI Lambertsons

Recycler Lamb.

Pbar Ext to RRPbar Inj from RR

Abort

NuMI

Pbar Ext to TeVQ1 = Q cos

Q2 = Q sin

Q1 = Q cos

Q2 = Q sin QXR/bucker

Extraction element Layout (what’s where}


Dave Johnson 3

LLambertson

Scanning Target

Septa

Q521

Q520

MI52 Extraction Region Physical Layout


Dave Johnson 4

Present parameter space of the resonant extraction process is based upon an analytical analysis and numerical simulation carried out by John Johnstone (1993)*. I want to introduce some of the design parameters he used (without going into detail).Initial tune separation, , of 0.015 as determined by current in the main

Quad bus. = (53/2 -

Harmonic phase, , as determined by the currents in the 2 familiesof harmonic quads QC206 -> coos( and QC328 -> sin(. where

= tan-1(as/qc) with q = SRQT(qs2 +qc

2) , where as and qc are the orthogonal sin and cos quad contributions

Currently, we are using only the cos family which produces the phasespace orientation seen in the following slide

Resonant Extraction parameters

*Beams-doc-092v2 and 096v1


Dave Johnson 5

Normalized Phase Space *

* Used in Johnstone’s analysis

Step size

Position of septa


Dave Johnson 6

Phase Space Orientation

Current Operation, Qc only Mixing Qs and QcReduces maximum beamSize around the ring


Dave Johnson 7

Step size, at the septa for the given by

= 2 sin-1{ (-cos(SQRT[1 + ( sin(

For the choices of and the current step size is ~3-4 mm (as confirmed by the beam distribution on MW702 which is approximately 180 deg in phase). Want to measure with TAR521

The 0th harmonic octupole, is the integrated octupole field aroundthe ring from the MI quads and trim octupoles. Early in the design(when IQC & IQD) were being constructed it was thought that the 0th Harmonic octupole family would be needed. Currently only the natural octupole content of the quads is being used. Re-measure tune shift due to octupoles---

Parameters, continued


Dave Johnson 8

With the these parameters fixed (i.e. and the followingparameters are determined.

The septum offset, x sep , is determined by

x sep = SQRT(sin(sin(

was selected to be 16 mm, but was reduced to ~ 13 mm to reduce themaximum beamsize elsewhere in the ring

This is determined by the closed orbit and the septa position, both Relative the the straight section.


Dave Johnson 9

The septa high voltage is100 kV which produces a Kick of 218 ur each or 436 ur.

Separation at Lambertson ~11 mm

Beam Separation at Septa


Dave Johnson 10

Impact of Septa High Voltage on 8 GeV Beam

Observations:•Orbit distortions•Tune shifts•Losses/ acceleration efficiency•Lattice perturbation

Loss at 608

Loss on MI52 kicker

Position at HP520

Beam

50kV

0kV

100 kV


Dave Johnson 11

Horizontal Orbit Distortion at 8 GeV vs Position at HP520 with Septa at 100 kV

y = 0.035x + 1.0852

0

0.2

0.4

0.6

0.8

1

1.2

1.4

-20 -15 -10 -5 0 5

Position at HP520 [mm]

X (rm

s) [m

m]

Impact of Septa High Voltage on 8 GeV Beam: Orbit Distortions

•Kick required to produce observed rms distortionx rmsrms

sqrt(sin(

•Measure orbit distortion at different offsetswith septa HV off and 100 kV

What septa voltage would be required to produce this kick? H.V. [kV] = Q[ur]g[cm]E[gev]/L[cm]

Kick Required to Produce Ovserved RMS Orbit Error

y = 0.0756x - 1E-16

00.010.020.030.040.050.060.070.080.090.1

0 0.2 0.4 0.6 0.8 1 1.2 1.4

RMS orbit error [mm]

Kic

k [m

r]

Measure ~76 r effective kick per mm of rms Distortion.

Range from 1 to 2.8 kV effective leakage over theRange between 12 and 32 mm => 0.9 kV/cm gradient


Dave Johnson 12

Impact of Septa High Voltage on 8 GeV Beam: Tune Shift

Tune shift at 100 KV vs HP520

-0.015

-0.01

-0.005

0

0.005

0 5 10 15 20

HP520 [mm]Tu

ne

Hor tune

Ver tune

Measure the tune as a function of position from the septa with the Septa HV at a constant 100 kV.

q where q = G dl [m-1]

A tune shift of 0.01 could be generatedby a quad strength of 0.003 [m-1] at a of 40 m

The tune shift due to s single quad errormay be estimated by:


Dave Johnson 13

Impact of Septa High Voltage on 8 GeV Beam: Lattice Distortion

Vertical Delta Beta vs Position with Septa at 100 KV

-0.3-0.2-0.1

00.10.20.30.40.5

-3 -6 -8

-12

-15

-18

Position at HP520 [mm]

dB

eta

/Be

ta

V517

V521

V609

V519

V523

V607

Vertical Beta Distortion with Septa at 100 kV

-0.2

0

0.2

0.4

Location

delta

Bet

a/B

eta -3 mm

-6 mm

-8 mm

-12 mm

-15 mm

-18 mm

qwhere qG L [m-1] sqrt(sin(2

Measure Lattice with Septa at 100 kV as a function of separation from septa.

The rms distortion due to a gradient error appears as a distortion at twice the betatron phase

To produce a of .2 from a single gradient error located at the septa with a of 40 m and a fractional tune of .42 requires a quad strength q of ~ .0067 [m-1] = > equivalent to about 6 amps on single harmonic quad at 8 GeV


Dave Johnson 14

Current mitigation•Move beam at HP520 to –18 mm (-15mm at septa)

when the septa HV is on and at nominal position for extraction

•Problem with this is that 8 GeV beam scrapes on upstream end of first 52 kicker

Short term solution (testing)•Reduce offset to –10 to –12 mm at HP520•Ramp septa from ~60 kV to 100 kV

•Power supply modificationsLonger term solution

•Fix position at HP520 for all cycles•Install vertical harmonic quads •Specialized three bump

Impact of Septa High Voltage on 8 GeV Beam: What to do ?


Dave Johnson 15

Flattop Orbits Used for Slow Spill

Horizontal Vertical

High field orbit and locations of tight aperture: remove momentum offset on stacking cycle -> smooth the 120 energy orbit Use time bumps to establish extraction orbit – problems with total required corrector current -- see next


Dave Johnson 16

Losses during slow spill

Losses on the septa and extractionLambertson

Losses at other tight apertures around the ring corrector quad moves large aperture quads

LN520E loss on downstream end of septa


Dave Johnson 17

IDHK104-0, strength from rotating coil

0.00

0.05

0.10

0.15

0.20

0.25

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0

current, A

inte

gral

(B*d

l), T

esla-

met

ers

IDHK104-0 (with cooling plates)IDH104-0 (original, without plates)Series4

• Current situation– Currently 35 correctors with FT time bumps– Five 30 Amp supplies– Eight 20A are > 80% Imax – One 30A > 80% Imax– H corr saturate above 15A. ->(11 corr > 15 A)

• Plans– MTF tests to add steel to reduce saturation effects (NuMI)– Add additional 30 Amp correctors– Quad moves to reduce corrector strength for slow spill– 453 card modifications (saturation lookup)

Flattop Orbit: Correctors


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Contributions to Horizontal tune at flattop

•Main quad bus: Qh (52 quads: 32-84”/8-100”/ 12-116”)Current 2826 amps for nom tune of 26.42 inc. to .485 requires ~ 4.4 ampsImplies 0.0136 /amp on the Qh bus. measured = 0.0146 / amp

2831 A => B’ = 163.08 kG/m => B’L/([m-1]

•Octupoles: in MI quads & 54 trim octupoles: 0th Harmonic Trim: b3Leff=29.72 [kGm/m3/A] => B’”L/([m-3] @ 10A In Quad: 5 units (E-5 of B’) => B’”L/([m-3] produce amplitude dependent tune shift ~ x2

•QXR: (Two 1 m air core configured in 0th harmonic) :

•Harmonic Quads: 2 families each with 8 magnets: 53rd Harmonic B’L = 0.0269 [T/amp] => B’L/([m-1] 8 GeV & 0.67E-4 @ 120 GeV {Implies = 0.004 / amp (if powered individually and not in family) measured = 0.0037 +/- 0.00067 / amp}

Each magnet measured B’L = 0.0066 [T/amp] => B’L/([m-1]

Implies 0.00012 /amp (for 2 mag) , measured = 0.001 /10 amp


Dave Johnson 19

Qh average current level changes of as little as 100 mA change extraction rate. => ~ 0.0015

Flattop Tune Regulation

Multiple cycles within an asymmetric TLG dueto changing bus resistance.

EE Support implementinga feedback system to measure changes in busresistance by monitoringmagnet power (i2r)

Status: In progress Implemented-3/31

100 mA/div


Dave Johnson 20

Slow spill regulation : QXR

QC206 harmonicquad ramp

QXR start level

Ideal spill


Dave Johnson 21

RF Spill

Scope pict. from Peter Prieto

What should we see on the RF spill monitor? With 30 bunches in the MI we should see600 ns burst of 53 Mhz (corresponding to the 30 bunches) repeating 11 us for the duration of the spill, currently 400 ms.

What do we see ?

Clumps of beam every whichlook to be harmonics of 60 Hz.

What about this frequencyStructure in the spill?

Tune or orbit modulationor modulation if the tune distribution?


Dave Johnson 22

RF Spill

We want a constant rate of extracted beam dN/dt, modulo the MI filling factor (i.e number of bunches) obtained by smoothly moving thebeam thru the ½ integer resonance stopband (QXR as 0th harmonic).

The tune spread of the beam is dN/dand d/dt is the rate of changeof the tune, where

d/dt = d(0)/dt +d(n)/dt , where d(0)/dt is provided by QXR, andd(n)/dt is unwanted tune modulationThen,

dN/dt = (dN/d)*(d/dt)

Either a modulation in dN/dor d/dt will produce unwantedspill modulation

RF Spill monitor located at F11


Dave Johnson 23

RF Spill

The tune spread, dN/d, is assumed to be gaussian with contributions from nonlinearities in magnet fields (i.e. octupole which produce x2) energy spread (chromaticity, p/p) -> large sync oscillations.

The sync frequency at 120 GeV is 192 Hz. A large sync oscillation could modulate tune spread in presence of large chromaticity.A preliminary investigation by varying fs between 100 and 240 Hzdidn’t change the observed freq modulation of the spill…

The sources of unwanted tune modulation, d(n)/dt need to be identified and reduced or eliminated. Some potential sources are:

The remaining tune modulation will be reduced by the bucker system. This work has just began…

Power supply ripple (Main and trim supplies) Main Supplies (bend and quad bus) Trim supplies ( correctors and harmonic quads)Mechanical vibrations


Dave Johnson 24

RF Spill Quality

120 Hz

800 Hz

What frequency structure is present in the spill ?

An FFT was performed on the signalfrom the RF spill monitor…

The predominate frequency was 120 Hz with nothing above 800 Hz

Look at only low frequencies <250 Hz

120

60 180

240

140

2kHz


Dave Johnson 25

100 ma/div

QXR20A FS

RFSPILL

MHIERR

Beam

Typical Spill with 1 turn 30 bunches:

Recall, that the horizontal quad bus produced a measured tune shift of0.0146 /amp => 70 mA will produce a 0.001 tune shift which is the equivalent to 10 amps on QXR (2 magnets).

RF Spill


Dave Johnson 26

RF Spill Quality - the Bucker

The Bucker system will be configured with two fast air core quads operatingon the 0th harmonic of the tune and have the capability xx amps with abandwidth of ~ 800 Hz.

The current bucker algorithm uses a moving average of three cells in a feedback and learn. This was used successfully in Tev but has not beenable to be used due to the large tune modulation.

A study has been proposed by Peter Preito to characterize the frequencyresponse of the MI during slow spill for selected freq between DC and 600 Hz. The purpose of this will be to generate coefficients to be usedAs a basis for the coefficients in the Bucker feedback algorithm.

The new bucker algorithm is based upon a least mean square adaptive noiseCanceling algorithm – already in use in MECAR.

Software modifications Required to Implement the new algorithm

Study time will be required… stay tuned…


Dave Johnson 27

S:HP3US ramp time can be remedied by three options:new transformer (more volts) – 9 mo + $add 2nd supply- complicatedmodify ramp (raise rest level/remove undershoot)

Keep rms < 900 Ampstime reduced to 1.7 sec. ramp + FT time (2.45 sec)

Current TLG module length is 3.6 sec…. can be shortened•The MI ramp length 2.78 sec (.5 sec inj , 1 sec FT)•S:HP3US ramp length is 3.6 sec (limiting factor)

How do slow spill cycles fit within the Program

-Minimize impact on Run II and stacking-Maximize beam to users

It will be an optimization of:number of cycles per min in the timelinethe spill lengthand bunch structure (i.e. number of bunches)


Dave Johnson 28

Current Flattop timing for Resonant Extraction

Harmonic quads• ½ int. comp• shrink phase space

MI Energy

Dipole Corrector (time bump)

Compatible with Mixed-mode Operation

QXR

Qh (26.42->.485)

Pbar prod. (1.22 sec)

Fast1.5 sec

Slow Spill start1.75 sec (400 ms)

Flattop 1.18 sec -> 2.18 sec

By removing the spilllength could be increasedby 250 –300 ms


Dave Johnson 29

•Set tune to .485 at start of flattop..•Assume 1 sec flattop length…•Min. delay from start of flattop ~ .32 sec (for dipole

and harmonic correctors to ramp) => max .68 sec spill

1 batch - cycle time would be ~2.53 sec limited by HP3US ramp time

6 batches* - cycle time is still 2.78 sec limited by MI ramp

Dedicated Slow Spill Cycle

* Multibatch operation needs Booster notcher working


Dave Johnson 30

1 batch + 1 batch -> MI cycle 2.53 sec (set by HP3US FT) 1 batch + 5 batch -> MI cycle 2.78 sec

In order to implement mixed mode we willrun stacking and slow spill with same lattice in P1 and P2

or create dual flattop power supply ramps and define an additional clock event to uniquely define this mode stacking $29/$80/$89 (for the beamline only)

slow spill $21/$30 mixed mode $21/$30/$80 (for Debuncher) and need multibatch injection !!!!!

Mixed Mode Cycle (with stacking)

Could be used in either dedicated or mixed mode (depend on TLG module)


Dave Johnson 31

Summary

Resonant extraction is being established and turned off on a regular basis by Operations via the Sequencer.Initial parameters sufficient to provide resonantly extracted beamto Experiments. these need optimized

Septa separationPhase space orientationMachine aperture / correctors / Large aperture quads

Instrumentation still needs to be fully commissioned and utilizedResonant BPM, loss monitor for TAR521Spill stability / quality issues are beginning to be addressed

Power supply/ RF/ Bucker algorithms Operational modes need to be defined (dedicated/mixed)

Most of the studies relating to optimizing resonant extraction may be carried out parasitically, but some will require dedicated study time with respect to Run II.

On-line resonant extraction simulation development continues

Documents

Extraction element layout Extraction parameters Current status of